Influence of external pressure on transcutaneous oxygen tension and laser Doppler flowmetry on sacral skin

The effects of external pressure upon transcutaneous oxygen tension (tcpO2) and skin blood flow (SKBF) over the sacral area were studied in 16 healthy volunteers. Pressure was applied on the sacral area using a special device which included tcpO2 and laser-Doppler flowmetry probes. The mean values of tcpO2, SKBF and wave occurrence of the flow were analysed for 18 increasing pressure levels. A significant decrease of tcpO2 was observed from 40 mmHg (5.3 Kpa) of applied pressure, while we obtained a significant decrease of SKBF when the external pressure was at 20 mmHg (2.7 Kpa). Using a non-linear regression model, we have found a fourth degree polynomial to describe the relationship between tcpO2 and SKBF according to increasing pressure. SKBF slow wave occurrence decreased when external pressure was at 10 mmHg (1.3 Kpa), while rapid wave occurrence significantly decreased only at 120 mmHg (16.1 kPa) pressure.